Portable drum-type surface-treating tool

ABSTRACT

A portable surface-treating tool including a drum which is driven rotatively by a motor, and is mounted for its desired rotation relative to a body of the tool by bearings located at opposite ends of the drum, and which carries a sheet of sandpaper or other surface treating material about the drum for contacting a work surface. The sandpaper sheet is desirably of a length to extend approximately one complete turn about the drum and is secured to the drum in a manner enabling removal and replacement of the sandpaper without partial or complete detachment of the drum or its bearings from the body of the tool.

United States Patent [72] Inventor Alma A.l'lutchins 49 N. Lotus, Pasadena, Calif. 91107 {21] AppLNo. 17,478 [22] Filed Mar.9, 1970 [45] Patented Aug.3,1971

[54] PORTABLE DRUM-TYPE SURF ACE-TREATING TOOL 22 Claims, 11 Drawing Figs.

[52] U.S.Cl 51/170, 51/364 [51] lnt.Cl ..B24b23/00 [50] FieldofSearch 51/170. 170.1,364,365,366 367,368,369,370,371; 143/431438 [56] References Cited UNITED STATES PATENTS 134,134 12/1872 Edwards 51/367 967,079 8/1910 Stipe 51/367 982,774 1/1911 Bagalio... 51/367 1,390,501 9/1921 Clarke.... 5l/170.1 1,540,591 6/1925 Barker 5l/170.1 1,604,677 10/1926 Brandsletter 51/365 1,660,015 2/1928 Schimpff 51/170 1,727,718 9/1929 Kinsey 5 H1701 1,952,385 3/1934 Morlock 51/364 2,220,370 11/1940 Hilger etal. 5l/364 2,259,685 l0/l94l Elsloo 5 H364 2,545,659 3/1951 Ginter 5 l/l70.l 2,982,059 5/1961 Trussell 51/371 3,395,495 8/1968 Powanda.... 5 1/1 70.1 3,468,073 9/1969 Del Vecchiou 51/l70.l 3,510,989 5/1970 Tolle 5l/l70.1

Primary ExaminerWilliam R. Armstrong Attorney-William P. Green ABSTRACT: A portable surface-treating tool including a drum which is driven rotatively by a motor, and is mounted for its desired rotation relative to a body of the tool by bearings located at opposite ends of the drum, and which carries a sheet of sandpaper or other surface treating material about the drum for contacting a work surface. The sandpaper sheet is desirably of a length to extend approximately one complete turn about the drum and is secured to the drum in a manner enabling removal and replacement of the sandpaper without partial or complete detachment of the drum or its bearings from the body of the tool.

PATENIED AUG 3197:

SHEET 1 BF 2 3,596fll1 1 HUTCH/AI QTTO'QAJEY PORTABLE DRUM-TYPE SURFACE-TREATING TOOL BACKGROUND OF THE INVENTION The invention relates generally to portable surface-treating tools, such as sanders and other abrading tools, polishing units, and the like. For simplicity of discussion, the invention will typically be described primarily as applied to sanding tools, though the broader applicability of the invention to polishers, etc. will be apparent without further elaboration.

There have in the past been proposed sanding tools of a type having a rotatable drum or drumlike element about which an abrading material is carried. For example, in Del Vecchio US. Pat. No. 3,468,073 issued Sept. 23, I969, there is disclosed a rotating element formed of rubber and about which an annular loop or belt of sandpaper is carried. However, removal and replacement of the belt of Del Vecchio requires dismantling of one of the bearings which mounts the rubber element, and the tool is therefore completely impractical for actual use in any commercial surface treating operation. Further, such belts are very expensive to purchase as compared with conventional flat sheet form sandpaper. Other drum-type sanding devices have been proposed in the past in which an elongated strip of sandpaper has been wound in roll form within the interior of a hollow drurn structure and an end portion of that strip has then been pulled out through a slit in the periphery of the drum to extend about it for contact with a work surface. This arrangement has had various disadvantages, including the requirement that a user have access to the interior of the drum for initially connecting the strip thereto, and including excessive complexity in cost of the drum structure, the difficulty of giving to the hollow drum and its related parts adequate structural strength to withstand the forces encountered in use, excessive cost of the specially formed wound strip form abrasive material, and other similar disadvantages.

SUMMARY OF THE INVENTION The present invention provides a unique drum-type portable sanderor the like in which removal and replacement of the sandpaper or other surface-treating material is extremely simple and can be attained without requirement for dismantling any of the bearings or other drum-mounting portions of the tool. Additionally, the tool is designed to utilize as the surfacetreating material sandpaper or other sheet material in its most basic and least expensive form, that is, in the form of conventional preferably standard size rectangular flat sheets of such material. These sheets can be attached to the drum rapidly and positively while the tool remains fully assembled, and without the complexities and problems inherent in use of the above discussed previously devised types of drum sanders.

The abrasive material or other surface-treating sheet material is desirably dimensioned to extend about the drum through approximately one single complete turn, and to have opposite end edges of the sheet received close together at a predetermined side of the drum. Desirably, means are provided for retaining both of these edges of the sandpaper to the drum to hold the paper in its active position of extension about the drum. One of the end edges may be secured by a clamping mechanism, which. tightly grips the material and holds it in fixed position until released. This clamping mechanism may be located within a recess or groove formed in the periphery ofthe drum, and may include a clamping element actuable by one or more fasteners, such as suitable screws or other threaded elements. In the presently preferred arrangement, the second end of the sheet material is secured to the drum by an adhesive substance, with the extremity of the second end preferably extending across the mentioned recess in the drum and slightly circularly overlapping the first mentioned end of the paper, to present a circularly complete "outer work contacting surface.

The body of the tool may carry the driving motor at one'end of the rotating drum or roller, and may include a shroud extending about one side of the drum-and leaving the other side of any of that air toward or past the work surface, to thusavoid blowing of any abraded work material, .dust,

powder, or the like into the surrounding air.

BRIEF DESCRIPTION OF THE DRAWINGS The above and other features and objects of the invention will be better understood from the following detailed description of the typical embodiment illustrated in the accompany ing drawings in which:

FIG. 1 is a perspective view showing a preferred forin of drum-type sander constructed in accordance with the invention; 1 I i s FIG. 2 is a perspective view showing the underside of the FIG. 1 tool;

FIG. 3 is a side view of the tool, taken on line"3-=3 of FIG. 1, but partially broken away to reveal the roller;

FIG. 4 is a fragmentary enlarged vertical section taken on line4-4ofFIG.1;

FIG 3 is a fragmentary enlarged vertical section taken on line5-5ofFlG.2;

FIG. 6 is a view showing the mounting for the outer handle ofthe device, and taken primarily on line 6-6 ofFIG. 3;

FIG. 7 is a section taken on line 7-7 of FIG. 4,

FIG. 8 is a horizontal sectiontaken on line 8-8 of FIG. 7;

FIG. 9 is an enlarged fragmentary vertical section through the lower portion of the drum, and takenon line 9590f FIG. 8;

FIG. 10 is a fragmentary vertical section taken on line 10-10 of FIG. 3, and;

FIG. 11 is a fragmentary section taken on line 11 11 of FIG. 10.

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring first to FIG. 1, I have shown at 10 a portable drum-type sander constructed in accordance with the invention, and including a main rigid body structure 11 to which there is mounted rotatively a drum or roller 12 which turns about an axis 13. The drum is driven by a motor 1.4, and the tool is held and manipulated by two handles 15 and 16,

The body 11 of the tool includes a hollow rigid housing 17 within which the mentioned motor 14 is carried, and includes also an elongated shroud 18 secured to and projectingfrom housing 17 and extending about the upper side of the drum. Housing 17 may be approximately circular in vertical section, and has the first handle 15 mounted to its upper side as shown.

More particularly, handle 15 may be a [loop type handle, havoperates a switch or valve 25, or the like, for controlling the. delivery of electric or pneumatic power from a supply line 26- to motor 14. In the presently preferred arrangement, motor 14 is an electric motor, in which event unit 25 is an electrical switch acting to close the circuit to the motor from supply line 26 upon actuation of the trigger.

The motor 14 has a driven shaft 27 mounted by bearings 28 to turn about an axis 29 which in the FIG. 3 orientation of the tool is disposed horizontally. This rotary shaft acts through a reduction gear assembly 30 to drive an. output shaft 31 rotatively at a reduced rate of speed about the previously. mentioned main axis 13, which main axis is parallel to axis 29 and like it disposed horizontally in the FIG. 3 normal orientation of the tool. The reduction gear assembly 30 may include a first pinion gear '33 mounted to and turning with motor shaft 27, and a second and larger pinion gear 34 meshing with and driven by gear 33 and mounted rigidly to shaft 31 to drive it.

The reduction gears are contained within a forward portion of the previously mentioned motor housing 17, and the output shaft 31 is mounted to that housing for rotation about axis 13 by appropriate bearingstypically represented at 35 and 36 in FIG. 3. I I

Drum 12 is driven rotatively by reduced speed shaft 31, and carries about its periphery a sheet of sandpaper or other surface-treating material 37, for contacting and abrading or otherwise treating a work surface 38'. This work surface may for example be a contoured portion of an automobile body, which is being sanded in preparation for repainting. The drum 12 has an inner rigid drum body 38 which may be formed as an extrusion having along its entire length the cross-sectional configuration illustrated in FIG. 7. Preferably, the drum body 38 is formed of an appropriate aluminum alloy having sufficient strength to withstand the forces encountered in use, and yet having a minimum of weight. To define the cross section of FIG. 7 somewhat more specifically, the extrusion forming body. of the drum or roller may have an outer essentially circular peripheral portion 39 presenting an external straight cylindrical outer surface 40 centered about and elongated in the direction of horizontal axis 13. This outer portion 39 of the drum is connected to an inner essentially cylindrical and tubular hub portion 41 by a number of radially extending webs 42, 43, and 44, the'latter of which may be thicker than the other two to contain mechanism fol-gripping an edge of the sandpaper sheet 37. The weight of the thicker web 44 and its related parts is counterbalanced by an axially extending lug or enlargement 145 at adiametrically opposite location in the drum. and in' a relation such that the entire drum and its carried sandpaper and all of the later-to-be-described parts which turn with the drum are precisely balanced rotativcly about axis 13. 1

For cushioning the contact of the sandpaper with a work surface, thedrum body 38 may carry about its periphery a cylindrical cushion 45 which may be formed of rubber or other cushioning material, and which has its inner surface 46 cemented securely and continuously to the outer surface of portion 39 of the drum. The outer surface 47 of cushioning element 45 is substantially cylindrical about axis 13, but may be slightly irregularized. v

The sheet of surface-treating material 37 may be a conventional rectangular standard size sheet of sandpaper, typically 9 inches by l 1 inches. having a first dimension which is equal to the axial length of drum 12, to extend along the entire axial length of the drum, and having a second dimension which is approximately equal to the circumference of the drum, to extend circularly entirely about the drum. More specifically, the second mentioned dimension of the sheet of sandpaper should preferably be just sufficiently greater than the circumference of the outer surface 47 of the drum cushion to allow for extension of one end edge 50 of the sheet into a recess or groove 48 in the drum, and to allow for slight circular overlapping of the other edge at 49. These two edges 49 and 50 of the sheet of sandpaper extend parallel to axis 13 of the drum in the P10. 7 condition of use of the apparatus.

The groove 48 in the drum is of uniform cross section along the entire length of the drum, which cross section is brought out beat in FIG. 9. The groove has a narrow radially extending portion 51 which extends inwardly through an interruption in the outer cushion 45, and into the thickened radial web portion 44 of the aluminum body of the drum to communicate at its radially inner end with an enlarged portion 52 of the recess or groove. Within portion 52, there' is positioned an axially elongated rigid clamping tube 53, which extends the entire length of the drum and groove, and which is actuable from the tion of one end of the sandpaper against a curved sidewall 54 of the recess or groove. Tube 53 is externally cylindrical along its entire length. and has a curvature corresponding to that of the curved sidewall portion 54, so that the paper is tightly clamped in a curving condition acting to very effectively retain that edge of the paper inthe groove and against separation from the roller.

The tube is normally yicldingly urged or biased to its full line retracted position of FIG. 9 by two wire springs 55 located at opposite ends of the drum. Each of these springs extends partially about an axially projecting end portion 56 of the drum, and may be received within and located by an annular groove 57in that portion 56, and has a first turned end 58 engaging one of the webs 43 of the drum, and a second end 58' turned axially and projecting axially into an end of tube 53 to urge that tube rightwardly in FIG. 9 to the full line position. The tube 53 is actuable leftwardly in FIG. 9 by a pair of actuating screws 59, which are mounted threadedly within passages 60 formed in the metal of drum body 38, and which extend transversely of the drum and of tube 53. As scenbest in FIG. 8, tightening of the screws will move tube 53 to its broken line clamping position of FIG. 9, while loosening of the screws enables the tube to be retracted to its full line FIG. 9 position in which a coacting edge of the sandpaper sheet 37 may be withdrawn from groove 38 or reinserted into that groove to clamping position. v

The second end of the sandpaper sheet, near its edge 49, is preferably secured to the drum by provision of a tacky adhesive material 61 on the cushion 45 at the location illustrated in FIG. 7, and preferably extending along the entire axial length of that edge of the cushion. This adhesive material may be any suitable substance capable of tightly but releaseably' retaining a sheet of sandpaper, such as for example a suitable feather edging cement, that is, a nonhardening permanently tacky contact cement capable of tightly retaining a sheet of sandpaper and yet permitting the paper to be stripped from the adhesive and from cushion 45 for replacement. One such feather edging cement on the market is that sold as '3-M Feather Edging Cement" by Minnesota Mining and Manufacturing Company.

After one edge of the sheet of sandpaper has been tightly retained in groove 48 by tube 53, the paper is pulled tightly about the drum and then adhered to adhesive 61,- with the second end of the sheet, adjacent its edge 49, projecting beyond adhesive 61 and across the entrance to groove or recess 48 and into the FIG. 9 slightly overlapping relation with respect .to the other end of the sandpaper. It is noted that tightening of the sandpaper about the drum, and particularly at and near the location 62 in FIG. 9 at which the sandpaper bends about the first edge of cushion 45, causes the cushion at this location to be slightly compressed radially inwardly to an extent corresponding approximately to the radial thickness of one layer of the'sandpaper, so that even though the second edge of the paper overlaps at this location it does not project radially outwardly beyond the level of the remainder of the paper, and in effect a continuous cylindrical sanding surface is presented to the workpiece.

Referring again to FIG. 3, it is apparent from that figure that the opposite ends of the drum, including both the drum, including both its inner metal body 38 and its outer cushion 45, are cut off transversely in planes 63 and 64 which are perpendicular to axis 13. At the end defined by plane 63, the previously discussed motor driven shaft 31 is connected to the drum in driving relation by connection of an externally threaded end 65 of the shaft into an internally threaded end portion 66 of the central axial passage 67 in the drum. To assist in centering these parts. shaft 31 may have an annular tapering surface 68 adjacent its threaded portion 65 which surface is engageable in annular seating relation with the correspondingly tapered surface 69 formed in the end of the drum. These two surfaces 68 and 69 are preferably tapered at a 45 angle with respect to axis 13, and of course are centered about that axis,

At its opposite end, the drum 12 may be mounted for rotation about axis 13 by a needle bearing 70 which is frictionally held within the left end of passage 67, and into which there projects an externally cylindrical stub shaft 71 carried by an end wall 72 of shroud 18. As will be apparent, this stub shaft 71 has a close rotary fit with the needle bearing 70 and is aligned with axis 13.

The shroud 18 extends approximately semicircularly about the upper half of the drum 12 in radially spaced relation thereto, to enclose the upper half of the drum and leave only its lower portion accessible for contact with a work surface. As seen best in FIG. 3, the shroud tapers progressively to a reduced diameter as it advances axially outwardly from the location of handle to the transverse end wall 72. At its opposite sides, the shroud terminates downwardly in a pair of parallel bottom edges 73 which are disposed parallel to axis 13 and are parallel to and spaced above the plane of work surface 38. At its right end as viewed in FIG. 3, the shroud is secured to housing 17 of the motor and reduction gear assembly by a plurality of screws 74, typically two such screws at each side of handle 15. These screws may extend into radially outwardly projecting bosses or lugs 75 formed on and integral with the housing 17, so that a right edge portion 76 of the shroud is received in radially spaced relation to an adjacent or opposed portion 77 of the outer surface of the motor housing (FIGS. 10 and 11), to define two spaces 78 at opposite sides of the handle and radially between the housing and shroud into' which motor cooling air from within housing 17 may flow upon leaving the housing through apertures 79 in the wall of the housing. This air enters the housing through an appropriate inlet 80 (FIG. 3), and then after flowing past the motor to cool it leaves the housing through openings 79 to enter one of the spaces 78 at opposite sides of the handle 15, and then flow rightwardly in FIG. 11 in a direction away from the sandpaper carrying drum. To prevent flow of any of this air from spaces 78 leftwardly toward the drum, housing 17 has a portion 81 (FIG. 11) which projects radially outwardly beyond the level of its previously mentioned portion 77, to contact the shroud and form an arcuate seal between the shroud and housing along the entire semicircular extent of the shroud between edges 73, with this seal functioning to prevent any movement of air leftwardly or rightwardly past the location 81 in FIG. 3. Thus, the entire circulation of motor cooling air is confined at the right side of the portion 81, to prevent this air from picking up or disturbing any of the abraded particles from the workpiece in the vicinity of the sandpaper or drum.

The wall 72 at the left end of the shroud may extend directly vertically or transversely of axis 13, and may have the stub shaft 71 secured rigidly thereto in any suitable manner, as by welding. Wall 72 preferably extends downwardly somewhat beyond the level of the two side edges 73 of the shroud, and may have a bottom semicircular edge 82 following generally the curvature of the drum, but of a diameter less than the periphery of the drum to avoid contact with the work surface.

Handle 16 is designed to project laterally with respect to axis 13 of the drum in either the leftward direction indicated by the full line position of FIG. I, or the rightward position represented in broken lines, to thus allow use of the device by either right-handed or left-handed persons. To enable such swinging movement of the handle between these two positions, the handle 16 is mounted pivotally as shown in FIG. 6. For this purpose, the handle has a mounting portion 83 containing a passage 84 receiving a vertically extending mounting shaft or pin 85 connected at its lower end to an upwardly deformed portion 86 of the top wall of shroud 18. The shaft or pin 85 may be appropriately welded or otherwise secured to the shroud, and has an upper threaded portion to which a nut 87 is connected to hold the mounting portion 83 of the handle between a pair of washers 88 in a manner confining the handle for only the desired swinging or pivotal movement between the two positions of FIG. 1. Nut 87 is a high-friction locknut which may be adjusted to lock the handle in any set position, or to offer a desired amount of frictional resistance to move ment of the handle.

In preparing the tool of the figures for use, an operator first releases the two screws 59 of FIGS. 7, 8 and 9 to a conditioncnabling retraction of clamping tube 53 to the full line posi-- tion of FIG. 9 by springs 55. The first edge of a sheet of sandpaper is then inserted into groove 48 in the position illustrated in FIG. 9, following which screws 59 are tightened to actuate clamping tube 53 to the broken line position of that figure, to thus tightly clamp and retain that edge of the paper in the groove. The paper is then pulled tightly about the drum and moved into contact with adhesive 61 near the opposite end of the sheet of paper, to thus hold the sheet in fixed position on the drum. A user may then grasp the two handles 15 and 16 in his two hands, and actuate trigger 24 to commence operation of the motor 14, and thereby commence rotation of the drum and carried sandpaper. The rotating drum is brought into contact with work surface 38' in FIG. 3, and performs an abrading operation thereon. The direction of rotation of the drum is in a clockwise direction as seen in FIGS. 7 and 9, so that the edge of the paper which is retained by the clamping structure is the circularly leading edge, and the overlapping edge 49 is the trailing edge. When it becomes necessary to replace the sandpaper, this may be done very easily by merely loosening the two screws 59 and pulling the used piece of sandpaper off of the drum, followed by attachment of a new and unused sheet of the same type to the drum in the manner previously discussed, and all without the necessity for even partial disassembly of the bearings and other structures which mount and drive the roller.

While a certain specific embodiment of the present invention has been disclosed as typical, the invention is of course not limited to this particular form, but rather is applicable broadly to all such variations as fall within the scope of the appended claims.

Iclaim:

l. A surface-treating tool comprising a portable body structure, a drum carried by said body structure for rotation relative thereto about an axis and containing a generally axially extending recess, first and second bearing means mounting opposite ends respectively of said drum to the body structure for rotation about said axis, a motor carried by the body structure and connected to the drum in rotary driving relation, means for securing to said drum for rotation therewith a sheet of sandpaper or other surface-treating material extending about the drum and having an edge projecting into said recess, and handle means for manipulating said body structure to bring said rotation sheet into contact with a work surface, said securing means including a clamping structure within said recess formed separately from said drum and elongated generally axially and movable transversely in the recess toward and away from an opposed surface between a gripping position in which it is tightened against and grips said edge of the sheet and a released position permitting withdrawal of said edge from the recess, and a plurality of threaded fasteners acting against said clamping structure at spaced locations and operable to actuate said clamping structure between said positions while said drum remains mounted at its opposite ends by said first and second bearing means.

2. A surface-treating tool comprising a portable body structure, a drum carried by said body structure for rotation relative thereto about an axis and containing a generally axially extending recess, first and second bearing means mounting opposite ends respectively of said drum to the body structure for rotation about said axis, a motor carried by the body structure and connected to the drum in rotary driving relation, means for securing to said drum for rotation therewith a sheet of sandpaper or other surface-treating material extending about the drum and having an edge projecting into said recess, and handle means for manipulating said body structure to bring said rotating sheet into contact with a work surface, said securing means including a clamping structure within said recess formed separately from said drum and elongated generally axially and movable transversely in the recess toward and away from an opposed surface between a gripping position in which it is tightened against and grips said edge of the sheet and a released position permitting withdrawal of said edge from the recess, and a plurality of threaded fasteners acting againstsaid clamping structure at spaced locations and operable to actuate said clamping structure toward said opposed surface and to said gripping position, while said drum remains mounted at its opposite ends by said first and second bearing means, there being springs at opposite ends of the drum engaging opposite ends of said clamping structure in a relation to yieldingly retract it away from said opposed surface.

, 3. A surface-treating tool as recited in claim 2, in which said clamping structure is a tube into the opposite ends of which said springs extend, said recess having a wall forming said op posed surface and curved essentially arcuately in essential correspondence with an external curved surface of said tube.

4. A surface-treating tool comprising a portable body structure, a drum carried by said body structure for rotation relative thereto about an axis and containing a generally axially extending recess, first and second bearing means mounting opposite ends respectively of said drum to the body structure for rotation about said axis, a motor carried by the body structure and connected to the drum in rotary driving relation, means for securing to said drum for rotation therewith a sheet of sandpaper or other surface-treating material extending about the drum and having an edge projecting into said recess, and handle means for manipulating said body structure to bring said rotating sheet into contact with a work surface, said securing means including a clamping structure within said recess formed separately from said drum and elongated generally axially and movable transversely in the recess toward and away from an opposed surface between a gripping position in which it is tightened against and grips said edge of the sheet and a released position permitting withdrawal of said edge from the recess, a plurality of threaded fasteners acting against said clamping structure at spaced locations and operable to actuate said clamping structure in a first direction relative to said opposed surface and between said positions while said drum remains mounted at its opposite ends by said bearings, and spring means yieldingly urging said clamping structure in theopposite direction relative to said opposed surface and between said positions.

5. A surface-treating tool as recited in claim 4, in which said fasteners actuate said clamping structure toward said opposed surface,,and said spring means yieldingly urge said clamping structure away from said opposed surface.

6. A surface-treating tool comprising a portable body structure, a drum carried by said body structure for rotation relative thereto about an axis and containing a generally axially extending recess, first and second bearing means mounting opposite ends respectively of said drum to the body structure for rotation about said axis, a motor carried by the body structure and connected to the drum in rotary driving relation, means for securing to said drum for rotation therewith a sheet of sandpaper or other surface-treating material extending about the drum and having an edge projecting into said recess, and handle means for manipulating said body structure to bring said rotating sheet into contact with a work surface, said securing means including a clamping structure within said recess formed separately from said drum and elongated generally axially and movable transversely in the recess toward and away from an opposed surface between a, gripping position in which it is tightened against and grips said edge of the sheet and a released position permitting withdrawal of said edge from the recess, said clamping structure having a recess extending into an end thereof, and a spring yieldingly urging said clamping structure in a predetermined direction relative to said opposed surface and having an actuating portion projecting into said recess in the clamping structure.

7. A surface-treating tool as recited in claim 6, in which said clamping structure is tubular and said recess forms a passage extending therethrough, there being two of said springs at opposite ends of the drum having actuating portions projecting generally axially into opposite ends of said tubular clamping structure.

8. A surface-treating tool comprising a portable body structure, a drum carried by said body structure for rotation relative thereto about an axis and containing a generally axially extending recess, first and second bearing means mounting opposite ends respectively of said drum to the body structure for rotation about said axis, a motor carried by the body structure and connected to the drum in rotary driving relation, means for securing to said drum for rotation therewith a sheet of sandpaper or other surface-treating material extending about the drum and having an edge projecting into said recess, and handle means for manipulating said body structure to bring said rotating sheet into contact with a work surface, said securing means including a clamping structure within said recess formed separately from said drum and elongated generally axially and movable transversely in the recess toward and away from an opposed surface between a gripping position in which it is'tightened against and grips said edge of the sheet and a released position permitting withdrawal of said edge from the recess, said opposed surface being located at a first side of said, clamping structure, and fastener means connected adjustably to the drum at essentially the opposite side of said clamping structure and exerting force against said opposite side in a relation to actuate said clamping structure toward said opposed surface and between said positions while said drum remains mounted at its ends by said first and second bearing means.

9. A surface-treating tool as recited in claim 8, in which said fastener means include a plurality of threaded fasteners connected threadedly to said drum at said opposite side of the clamping structure and exerting force adjustably against said clamping structure at axially spaced locations and toward said opposed surface.

10. A surface-treating tool comprising a portable body structure, a drum carried by said body structure for rotation relative thereto about an axis and containing a generally axially extending recess, first and second bearing means mounting opposite ends respectively of said drum to the body structure for rotation about said axis, a motor carried by the body structure and connected to the drum in rotary driving relation, means for securing to said drum for rotation therewith a sheet of sandpaper or other surface-treating material extending about the drum and having an edge projecting into said recess, and handle means for manipulating said body structure to bring said rotating sheet into contact with a work surface, said securing means including a clamping structure within said recess formed separately from said drum and elongated generally axially and movable transversely in the recess toward and away from an opposed surface between a gripping position in which it is tightened against and grips said edge of the sheet and a released position permitting withdrawal of said edge from the recess, said clamping structure having a surface facing said opposed surface in clamping relation, one of said surfaces being elongated axially of the drum' and curved transversely of its length and concavely to define a curved axially elongated recess, the other surface being also elongated axially of the drum and transversely of its length but convexly to clamp said sheet within said recess.

11. A surface-treating tool as recited in claim 10, in which said one of the surfaces is a sidewall of said recess, said other surface being an essentially cylindrical external surface on said clamping structure.

12. A surface-treating tool comprising a portable body structure, a drum carried by said body structure for rotation relative thereto about an axis and containing a generally axially extending recess having a relatively wide radially inner portion and a narrower entrance portion extending generally radially inwardly from the periphery of the drum to said wide inner portion of the recess, first and second bearing means mounting opposite ends respectively of said drum to the body structure for rotation about said axis, a motor carried by the body structure and connected to the drum in rotary driving relation, means for securing to said drum for rotation therewith a sheet of sandpaper or other surface-treating material extending about the drum and having an edge projecting into said recess, and handle means for manipulating said body structure to bring said rotating sheet into contact with a work surface, said wide inner portion of the recess hav' ing an axially elongated sidewall at one side thereof which is curved transversely of the drum and concavcly to define a curved axially elongated groove, said securing means including an axially extending clamping tube within said wide portion of the recess formed separately from the drum and movable transversely toward and away from said curved sidewall and having an outer surface curved generally in correspondence with said curved sidewall to clamp said sheet thereagainst; a plurality of axially spaced screws connected threadedly and adjustably into spaced passages in a second sidewall of said recess at a side of the recess opposite from that on which said curved first mentioned sidewall is formed and acting to tighten said tube against said first mentioned sidewall, said passages continuing outwardly to the periphery of the drum, said fasteners having tool actuable portions accessible through said passages from the periphery of the drum for adjustment of the screws, and a pair of springs connected to opposite ends of said drum and having ends projecting into opposite ends of said tube and yieldingly urging it away from said first mentioned sidewall.

13. A surface-treating tool comprising a portable body structure, a drum carried by said body structure for rotation relative thereto about an axis, first and second bearing means mounting opposite ends respectively of said drum to the body structure for rotation about said axis, a motor carried by the body structure and connected to one end of the drum in rotary driving relation, a first handle connected to the body structure near said one end of the drum to be grasped by a first hand of the user, a second handle near the opposite end of the drum to be grasped by a second hand of the user, and a pivotal connection attaching said second handle to said body structure for swinging movement between leftwardly and rightwardly projecting positions and about an axis which extends generally perpendicular to and which essentially intersects said firstmentioned axis.

14. A surface-treating tool as recited in claim 13, in which said body structure includes a shroud extending about and enclosing an upper side of the drum but leaving a lower side thereof exposed for acting on a work surface, said pivotal connection being carried at the upper side of said shroud near one end thereof.

15. A surface-treating tool comprising a drum mounted to turn about an axis and to carry a sheet of surface-treating material, an electric motor at one end of said drum and connected to said end of the drum in rotary driving relation, said motor having a housing containing air inlet and outlet openings for circulating cooling air through the interior of the housing, a shroud extending partially about said drum and carrying a bearing structure at an outer end of the shroud and drum to mount the drum for said rotation, said shroud having an inner end connected to said housing and projecting to a location axially overlapping but spaced radially outwardly from one of said air openings to confine and direct the air flowing therethrough, there being an air seal formed between said shroud and housing at a location axially intermediate said one opening and the interior of the shroud in a relation preventing flow of air between said one opening and the interior of the shroud.

16. A surface-treating tool as recited in claim 15, in which said shroud extends essentially semicircularly about and sub stantially semicircularly engages the periphery of said housing at the location of said air seal.

17. A surface-treating tool as recited in claim' 15, in which said housing has a first relatively large diameter portion engaged essentially semicircularly by said shroud at the location of said air seal, and has a reduced diameter portion therebeyond containing a plurality of said air openings at circularly spaced locations, said inner end of the shroud having an essentially semicylindrical terminal portion projecting beyond said air seal and overlapping but spaced radially from said plurality of openings re uced diameter portion of in ear the motor housing, said housing having lugs of increased diameter circularly between which said plurality of air openings are located and to which said shroud is connected.

18. A portable surface-treating tool comprising a drum mounted to turn about an an axis, means for detachably connecting a sheet of surface-treating material to said drum in a position of extension thereabout, a motor located at a first end of said drum and having a housing at said end and having a shaft driven by the motor and mounted by the housing to turn about said axis, interfitting threads on said shaft and said first end of the drum centered about said axis and detachably interconnectable by turning movement of the drum relative to the shaft to transmit rotation from the shaft to the drum, a shroud extending generally axially of the drum and disposed partially thereabout but interrupted at one side of the drum to expose the drum and a carried sheet of surface-treating material to act on a work surface, bearing means for mounting the second end of the drum to turn about said axis and including two interfitting bearing units carried by said shroud and the second end of the drum respectively and movable into and out of interfitting drum supporting bearing engagement by movement of one unit axially relative to the other, and means for connecting said shroud to said housing near said first end of the drum.

19. A portable surface-treating tool as recited in claim 18, in which said shroud has an outer end wall, one of said bearing units being a stub shaft carried by and projecting axially from said end wall of the shroud, the other unit being a bearing structure mounted in said second end of the drum and containing an axial opening into which said stub shaft is movable by axial movement of the shroud.

20. A portable surface-treating tool as recited in claim 19, in which said motor has an armature mounted to turn in said housing about a second axis parallel to but offset from said first axis, there being reduction gear means in said housing for driving said first mentioned shaft of claim 18 from said motor armature, said shroud having an end portion near said first end of the drum extending essentially about the location of said reduction gear means and connected to said motor housing by said connecting means essentially about said reduction gear means.

El. A portable surface-treating tool comprising a drum mounted to turn about an axis, means for detachably connecting a sheet of surface-treating material to said drum in a position of extension thereabout, a motor located at a first end of the drum and having a housing and an armature mounted to turn about an axis which is essentially parallel to but offset from said first mentioned axis, a shaft mounted by the housing to turn about said first axis and connectable to said first end of the drum in driving relation, gears in the housing for driving said shaft from said motor armature, a shroud extending generally axially of the drum and disposed partially thereabout but interrupted at one side of the drum, bearing means at the second end of the drum mounting said second end rotatably to an outer end of the shroud, said shroud having an inner end connected to said housing and extending partially about the location of said gears.

22. A surface-treating tool comprising a portable body structure, a drum mounted rotatably to said body structure, a motor for driving surface-treating drum, a sheet of surfacetreating material extending about said drum through essentially a single complete turn, said drum containing a recess extending generally axially therealong, means within said recess for releasably gripping and retaining a first edge of said sheet, and adhesive securing an opposite edge of the sheet to the drum adjacent said recess. 

1. A surface-treating tool comprising a portable body structure, a drum carried by said body structure for rotation relative thereto about an axis and containing a generally axially extending recess, first and second bearing means mounting opposite ends respectively of said drum to the body structure for rotation about said axis, a motor carried by the body structure and connected to the drum in rotary driving relation, means for securing to said drum for rotation therewith a sheet of sandpaper or other surface-treating material extending about the drum and having an edge projecting into said recess, and handle means for manipulating said body structure to bring said rotation sheet into contact with a work surface, said securing means including a clamping structure within said recess formed separately from said drum and elongated generally axially and movable transversely in the recess toward and away from an opposed surface between a gripping position in which it is tightened against and grips said edge of the sheet and a released position permitting withdrawal of said edge from the recess, and a plurality of threaded fasteners acting against said clamping structure at spaced locations and operable to actuate said clamping structure between said positions while said drum remains mounted at its opposite ends by said first and second bearing means.
 2. A surface-treating tool comprising a portable body structure, a drum carried by said body structure for rotation relative thereto about an axis and containing a generally axially extending recess, first and second bearing means mounting opposite ends respectively of said drum to the body structure for rotation about said axis, a motor carried by the body structure and connected to the drum in rotary driving relation, means for securing to said drum for rotation therewith a sheet of sandpaper or other surface-treating material extending about the drum and having an edge projecting into said recess, and handle means for manipulating said body structure to bring said rotating sheet into contact with a work surface, said securing means including a clamping structure within said recess formed separately from said drum and elongated generally axially and movable transversely in the recess toward and away from an opposed surface between a gripping position in which it is tightened against and grips said edge of the sheet and a released position permitting withdrawal of said edge from the recess, and a plurality of threaded fasteners acting against said clamping structure at spaced locations and operable to actuate said clamping structure toward said opposed surface and to said gripping position, while said drum remains mounted at its opposite ends by said first and second bearing means, there being springs at opposite ends of the drum engaging opposite ends of said clamping structure in a relation to yieldingly retract it away from said opposed surface.
 3. A surface-treating tool as recited in claim 2, in which said clamping structure is a tube into the opposite ends of which said springs extend, said recess having a wall forming said opposed surface and curved essentially arcuately in essential correspondence with an external curved surface of said tube.
 4. A surface-treating tool comprising a portable body structure, a drum carried by said body structure for rotation relative thereto about an axis and containing a generally axially extending recess, first and second bearing means mounting opposite ends respectively of said drum to the body structuRe for rotation about said axis, a motor carried by the body structure and connected to the drum in rotary driving relation, means for securing to said drum for rotation therewith a sheet of sandpaper or other surface-treating material extending about the drum and having an edge projecting into said recess, and handle means for manipulating said body structure to bring said rotating sheet into contact with a work surface, said securing means including a clamping structure within said recess formed separately from said drum and elongated generally axially and movable transversely in the recess toward and away from an opposed surface between a gripping position in which it is tightened against and grips said edge of the sheet and a released position permitting withdrawal of said edge from the recess, a plurality of threaded fasteners acting against said clamping structure at spaced locations and operable to actuate said clamping structure in a first direction relative to said opposed surface and between said positions while said drum remains mounted at its opposite ends by said bearings, and spring means yieldingly urging said clamping structure in the opposite direction relative to said opposed surface and between said positions.
 5. A surface-treating tool as recited in claim 4, in which said fasteners actuate said clamping structure toward said opposed surface, and said spring means yieldingly urge said clamping structure away from said opposed surface.
 6. A surface-treating tool comprising a portable body structure, a drum carried by said body structure for rotation relative thereto about an axis and containing a generally axially extending recess, first and second bearing means mounting opposite ends respectively of said drum to the body structure for rotation about said axis, a motor carried by the body structure and connected to the drum in rotary driving relation, means for securing to said drum for rotation therewith a sheet of sandpaper or other surface-treating material extending about the drum and having an edge projecting into said recess, and handle means for manipulating said body structure to bring said rotating sheet into contact with a work surface, said securing means including a clamping structure within said recess formed separately from said drum and elongated generally axially and movable transversely in the recess toward and away from an opposed surface between a gripping position in which it is tightened against and grips said edge of the sheet and a released position permitting withdrawal of said edge from the recess, said clamping structure having a recess extending into an end thereof, and a spring yieldingly urging said clamping structure in a predetermined direction relative to said opposed surface and having an actuating portion projecting into said recess in the clamping structure.
 7. A surface-treating tool as recited in claim 6, in which said clamping structure is tubular and said recess forms a passage extending therethrough, there being two of said springs at opposite ends of the drum having actuating portions projecting generally axially into opposite ends of said tubular clamping structure.
 8. A surface-treating tool comprising a portable body structure, a drum carried by said body structure for rotation relative thereto about an axis and containing a generally axially extending recess, first and second bearing means mounting opposite ends respectively of said drum to the body structure for rotation about said axis, a motor carried by the body structure and connected to the drum in rotary driving relation, means for securing to said drum for rotation therewith a sheet of sandpaper or other surface-treating material extending about the drum and having an edge projecting into said recess, and handle means for manipulating said body structure to bring said rotating sheet into contact with a work surface, said securing means including a clamping structure within said recess formed separately from said drum and elongated generally axIally and movable transversely in the recess toward and away from an opposed surface between a gripping position in which it is tightened against and grips said edge of the sheet and a released position permitting withdrawal of said edge from the recess, said opposed surface being located at a first side of said clamping structure, and fastener means connected adjustably to the drum at essentially the opposite side of said clamping structure and exerting force against said opposite side in a relation to actuate said clamping structure toward said opposed surface and between said positions while said drum remains mounted at its ends by said first and second bearing means.
 9. A surface-treating tool as recited in claim 8, in which said fastener means include a plurality of threaded fasteners connected threadedly to said drum at said opposite side of the clamping structure and exerting force adjustably against said clamping structure at axially spaced locations and toward said opposed surface.
 10. A surface-treating tool comprising a portable body structure, a drum carried by said body structure for rotation relative thereto about an axis and containing a generally axially extending recess, first and second bearing means mounting opposite ends respectively of said drum to the body structure for rotation about said axis, a motor carried by the body structure and connected to the drum in rotary driving relation, means for securing to said drum for rotation therewith a sheet of sandpaper or other surface-treating material extending about the drum and having an edge projecting into said recess, and handle means for manipulating said body structure to bring said rotating sheet into contact with a work surface, said securing means including a clamping structure within said recess formed separately from said drum and elongated generally axially and movable transversely in the recess toward and away from an opposed surface between a gripping position in which it is tightened against and grips said edge of the sheet and a released position permitting withdrawal of said edge from the recess, said clamping structure having a surface facing said opposed surface in clamping relation, one of said surfaces being elongated axially of the drum and curved transversely of its length and concavely to define a curved axially elongated recess, the other surface being also elongated axially of the drum and transversely of its length but convexly to clamp said sheet within said recess.
 11. A surface-treating tool as recited in claim 10, in which said one of the surfaces is a sidewall of said recess, said other surface being an essentially cylindrical external surface on said clamping structure.
 12. A surface-treating tool comprising a portable body structure, a drum carried by said body structure for rotation relative thereto about an axis and containing a generally axially extending recess having a relatively wide radially inner portion and a narrower entrance portion extending generally radially inwardly from the periphery of the drum to said wide inner portion of the recess, first and second bearing means mounting opposite ends respectively of said drum to the body structure for rotation about said axis, a motor carried by the body structure and connected to the drum in rotary driving relation, means for securing to said drum for rotation therewith a sheet of sandpaper or other surface-treating material extending about the drum and having an edge projecting into said recess, and handle means for manipulating said body structure to bring said rotating sheet into contact with a work surface, said wide inner portion of the recess having an axially elongated sidewall at one side thereof which is curved transversely of the drum and concavely to define a curved axially elongated groove, said securing means including an axially extending clamping tube within said wide portion of the recess formed separately from the drum and movable transversely toward and away from said curved sidewall and having aN outer surface curved generally in correspondence with said curved sidewall to clamp said sheet thereagainst; a plurality of axially spaced screws connected threadedly and adjustably into spaced passages in a second sidewall of said recess at a side of the recess opposite from that on which said curved first mentioned sidewall is formed and acting to tighten said tube against said first mentioned sidewall, said passages continuing outwardly to the periphery of the drum, said fasteners having tool actuable portions accessible through said passages from the periphery of the drum for adjustment of the screws, and a pair of springs connected to opposite ends of said drum and having ends projecting into opposite ends of said tube and yieldingly urging it away from said first mentioned sidewall.
 13. A surface-treating tool comprising a portable body structure, a drum carried by said body structure for rotation relative thereto about an axis, first and second bearing means mounting opposite ends respectively of said drum to the body structure for rotation about said axis, a motor carried by the body structure and connected to one end of the drum in rotary driving relation, a first handle connected to the body structure near said one end of the drum to be grasped by a first hand of the user, a second handle near the opposite end of the drum to be grasped by a second hand of the user, and a pivotal connection attaching said second handle to said body structure for swinging movement between leftwardly and rightwardly projecting positions and about an axis which extends generally perpendicular to and which essentially intersects said first-mentioned axis.
 14. A surface-treating tool as recited in claim 13, in which said body structure includes a shroud extending about and enclosing an upper side of the drum but leaving a lower side thereof exposed for acting on a work surface, said pivotal connection being carried at the upper side of said shroud near one end thereof.
 15. A surface-treating tool comprising a drum mounted to turn about an axis and to carry a sheet of surface-treating material, an electric motor at one end of said drum and connected to said end of the drum in rotary driving relation, said motor having a housing containing air inlet and outlet openings for circulating cooling air through the interior of the housing, a shroud extending partially about said drum and carrying a bearing structure at an outer end of the shroud and drum to mount the drum for said rotation, said shroud having an inner end connected to said housing and projecting to a location axially overlapping but spaced radially outwardly from one of said air openings to confine and direct the air flowing therethrough, there being an air seal formed between said shroud and housing at a location axially intermediate said one opening and the interior of the shroud in a relation preventing flow of air between said one opening and the interior of the shroud.
 16. A surface-treating tool as recited in claim 15, in which said shroud extends essentially semicircularly about and substantially semicircularly engages the periphery of said housing at the location of said air seal.
 17. A surface-treating tool as recited in claim 15, in which said housing has a first relatively large diameter portion engaged essentially semicircularly by said shroud at the location of said air seal, and has a reduced diameter portion therebeyond containing a plurality of said air openings at circularly spaced locations, said inner end of the shroud having an essentially semicylindrical terminal portion projecting beyond said air seal and overlapping but spaced radially from said plurality of openings in said reduced diameter portion of the motor housing, said housing having lugs of increased diameter circularly between which said plurality of air openings are located and to which said shroud is connected.
 18. A portable surface-treating tool comprising a drum mounted to turn about an an axis, means for detachably connecting a sHeet of surface-treating material to said drum in a position of extension thereabout, a motor located at a first end of said drum and having a housing at said end and having a shaft driven by the motor and mounted by the housing to turn about said axis, interfitting threads on said shaft and said first end of the drum centered about said axis and detachably interconnectable by turning movement of the drum relative to the shaft to transmit rotation from the shaft to the drum, a shroud extending generally axially of the drum and disposed partially thereabout but interrupted at one side of the drum to expose the drum and a carried sheet of surface-treating material to act on a work surface, bearing means for mounting the second end of the drum to turn about said axis and including two interfitting bearing units carried by said shroud and the second end of the drum respectively and movable into and out of interfitting drum supporting bearing engagement by movement of one unit axially relative to the other, and means for connecting said shroud to said housing near said first end of the drum.
 19. A portable surface-treating tool as recited in claim 18, in which said shroud has an outer end wall, one of said bearing units being a stub shaft carried by and projecting axially from said end wall of the shroud, the other unit being a bearing structure mounted in said second end of the drum and containing an axial opening into which said stub shaft is movable by axial movement of the shroud.
 20. A portable surface-treating tool as recited in claim 19, in which said motor has an armature mounted to turn in said housing about a second axis parallel to but offset from said first axis, there being reduction gear means in said housing for driving said first mentioned shaft of claim 18 from said motor armature, said shroud having an end portion near said first end of the drum extending essentially about the location of said reduction gear means and connected to said motor housing by said connecting means essentially about said reduction gear means.
 21. A portable surface-treating tool comprising a drum mounted to turn about an axis, means for detachably connecting a sheet of surface-treating material to said drum in a position of extension thereabout, a motor located at a first end of the drum and having a housing and an armature mounted to turn about an axis which is essentially parallel to but offset from said first mentioned axis, a shaft mounted by the housing to turn about said first axis and connectable to said first end of the drum in driving relation, gears in the housing for driving said shaft from said motor armature, a shroud extending generally axially of the drum and disposed partially thereabout but interrupted at one side of the drum, bearing means at the second end of the drum mounting said second end rotatably to an outer end of the shroud, said shroud having an inner end connected to said housing and extending partially about the location of said gears.
 22. A surface-treating tool comprising a portable body structure, a drum mounted rotatably to said body structure, a motor for driving surface-treating drum, a sheet of surface-treating material extending about said drum through essentially a single complete turn, said drum containing a recess extending generally axially therealong, means within said recess for releasably gripping and retaining a first edge of said sheet, and adhesive securing an opposite edge of the sheet to the drum adjacent said recess. 